Lactoperoxidase is an enzyme naturally found in milk, saliva, and other secretions. It is part of the peroxidase family of enzymes and is known for its antimicrobial properties. Lactoperoxidase is also used as a light stabilizer in certain cosmetic and pharmaceutical formulations due to its ability to protect light-sensitive ingredients from degradation caused by exposure to light. The enzyme acts by catalyzing the oxidation of hydrogen peroxide to produce oxygen and other reactive species, which can help in stabilizing formulations that are prone to light-induced damage.

Chemical Composition and Structure

Lactoperoxidase is a glycoprotein enzyme with a heme group at its active site, which facilitates the oxidation reactions. The enzyme utilizes hydrogen peroxide (H₂O₂) to catalyze the oxidation of various substrates, including glucose, leading to the generation of reactive oxygen species. The structure of lactoperoxidase includes:

• Heme group: A component essential for the enzyme’s peroxidase activity.
• Amino acids: The enzyme is composed of a sequence of amino acids, which make it a functional glycoprotein that can bind to hydrogen peroxide and substrates to carry out its oxidation functions.

Function as a Light Stabilizer

Lactoperoxidase can act as a stabilizer by mitigating the oxidative damage caused by exposure to light. Here’s how it works:

• Oxidative Protection: The enzyme helps reduce the generation of free radicals and other reactive species when products are exposed to light. By using hydrogen peroxide in a controlled manner, lactoperoxidase helps to protect sensitive compounds from photo-oxidation.
• Enhanced Stability: In formulations containing vitamins (such as vitamin C), antioxidants, or other light-sensitive ingredients, lactoperoxidase can prevent their degradation, helping maintain their efficacy and prolonging the shelf life of the product.

Applications

Cosmetics and Personal Care Products

• Stabilizing light-sensitive ingredients: Lactoperoxidase can be used in cosmetic formulations to prevent the degradation of sensitive ingredients when exposed to light, such as in facial creams, serums, or lotions containing active ingredients like vitamin C.
• Preservation and antibacterial effect: Due to its natural antimicrobial properties, lactoperoxidase is also utilized in products like mouthwashes, toothpaste, and skin cleansers to prevent bacterial growth and maintain product stability.
• Anti-aging products: It can be incorporated into anti-aging formulations to stabilize ingredients and protect them from oxidative damage caused by environmental factors, including light.

CAS Number: 9003-99-0
EC Number: 232-668-6

Food Industry

• Antimicrobial action: In the food industry, lactoperoxidase is often used as a preservative to inhibit bacterial growth and extend the shelf life of perishable products, especially in dairy products.
• Light protection in food: Lactoperoxidase can be used to stabilize light-sensitive compounds in foods that are exposed to light during processing or storage.

Pharmaceuticals

• Topical treatments: In pharmaceutical products, lactoperoxidase can be used in topical creams and ointments to stabilize light-sensitive ingredients and provide additional antimicrobial properties.
• Formulation stability: It can also be used to enhance the stability of pharmaceutical formulations, especially those that contain antioxidants or other light-sensitive substances.

Environmental and Safety Considerations

• Biodegradability: Lactoperoxidase is a natural enzyme and is biodegradable, making it environmentally friendly when disposed of properly.
• Safety Profile: Lactoperoxidase is generally considered safe for use in cosmetics, personal care, and food products. It has a low toxicity profile and is well tolerated in the concentrations typically used. However, individuals with allergies to milk or dairy proteins should exercise caution.
• Sustainability: As a naturally occurring enzyme, lactoperoxidase can be sustainably sourced, making it an eco-friendly choice for light stabilization in various products.

References__________________________________________________________________________

Kussendrager KD, van Hooijdonk AC. Lactoperoxidase: physico-chemical properties, occurrence, mechanism of action and applications. Br J Nutr. 2000 Nov;84 Suppl 1:S19-25. doi: 10.1017/s0007114500002208.

Abstract. Lactoperoxidase (LP) is one of the most prominent enzymes in bovine milk and catalyses the inactivation of a wide range of micro-organisms in the lactoperoxidase system (LP-s). LP-systems are also identified as natural antimicrobial systems in human secretions such as saliva, tear-fluid and milk and are found to be harmless to mammalian cells. The detailed molecular structure of LP is identified and the major products generated by the LP-s and their antimicrobial action have been elucidated for the greater part. In this paper several aspects of bovine LP and LP-s are discussed, including physico-chemical properties, occurrence in milk and colostrum and mechanisms of action. Since the introduction of industrial processes for the isolation of LP from milk and whey the interest in this enzyme has increased considerably and attention will be paid to potential and actual applications of LP-systems as biopreservatives in food and other products.

Flemmig J, Gau J, Schlorke D, Arnhold J. Lactoperoxidase as a potential drug target. Expert Opin Ther Targets. 2016;20(4):447-61. doi: 10.1517/14728222.2016.1112378. 

Abstract. Introduction: Lactoperoxidase (LPO) belongs to the immunologically relevant mammalian heme peroxidases. The enzyme contributes in external secretions to the humoral immune defense against pathogens by oxidation of thiocyanate (SCN(-)) and iodide (I(-)). The generation of oxidized thiocyanate and/or iodine species is also important in numerous biotechnological applications of LPO. Areas covered: In this review, we give an overview about the present knowledge of LPO concerning enzymatic structure, catalytic cycles and (pseudo-)halogenated species generated by the enzyme. Redox properties of LPO as well as kinetic aspects regarding the different enzymatic cycles are discussed in order to gain insights into the disturbance of the (pseudo-)halogenating enzyme activity under pathological conditions. Important structural features of LPO and crystallographic studies on the interaction and reaction of organic substrates with the enzyme are also summarized. A broad discussion is devoted to the binding and oxidation of substrates that either inhibit or promote LPO activity. Expert opinion: On the basis of these data, different strategies to further optimize LPO functions in humoral defense of mucous surfaces and biotechnological applications are discussed. In particular, hydrophobic organic substrates with a 3,4-dihydroxyphenyl partial structure considerably enhance the (pseudo-)halogenating activity of LPO. Their application provides, thus, a new strategy to enhance the anti-microbial activity of this enzyme.

Magacz M, Kędziora K, Sapa J, Krzyściak W. The Significance of Lactoperoxidase System in Oral Health: Application and Efficacy in Oral Hygiene Products. Int J Mol Sci. 2019 Mar 21;20(6):1443. doi: 10.3390/ijms20061443. 

Abstract. Lactoperoxidase (LPO) present in saliva are an important element of the nonspecific immune response involved in maintaining oral health. The main role of this enzyme is to oxidize salivary thiocyanate ions (SCN-) in the presence of hydrogen peroxide (H₂O₂) to products that exhibit antimicrobial activity. LPO derived from bovine milk has found an application in food, cosmetics, and medical industries due to its structural and functional similarity to the human enzyme. Oral hygiene products enriched with the LPO system constitute an alternative to the classic fluoride caries prophylaxis. This review describes the physiological role of human salivary lactoperoxidase and compares the results of clinical trials and in vitro studies of LPO alone and complex dentifrices enriched with bovine LPO. The role of reactivators and inhibitors of LPO is discussed together with the possibility of using nanoparticles to increase the stabilization and activity of this enzyme.

Köksal Z, Alim Z. Lactoperoxidase, an antimicrobial enzyme, is inhibited by some indazoles. Drug Chem Toxicol. 2020 Jan;43(1):22-26. doi: 10.1080/01480545.2018.1488861. 

Abstract. Lactoperoxidase (LPO) has bactericidal and bacteriostatic activity on various microorganisms and it creates a natural antimicrobial defense system. So, LPO is one of the essential enzyme in biological systems and the protection of the LPO activity is extremely important for the immune system. Because of these features, the protection of the activity of the LPO has vital importance for the health of the organisms. Also, LPO is used in various sectors from cosmetics industry to agriculture industry due to its broad antimicrobial properties. Therefore, the identification of inhibitors and activators of the LPO is becoming increasingly important. In present study we aimed to investigate the inhibitory effects of some indazoles [1H-indazole (1a), 4-Bromo-1H-indazole (2a), 6-Bromo-1H-indazole (3a), 7-Bromo-1H-indazole (4a), 4-chloro-1H-indazole (5a), 6-chloro-1H-indazole (6a), 7-chloro-1H-indazole (7a), 4-fluoro-1H-indazole (8a), 6-fluoro-1H-indazole (9a), 7-fluoro-1H-indazole (10a)] on bovine milk LPO. Indazole derivatives are heterocyclic organic molecules with a wide range of biological activity. For this aim, bovine milk LPO was purified using Sepharose-4B-l-tyrosine-5-amino-2-methyl benzenesulfonamide affinity chromatography method. Then, the potential inhibitory effects of indazoles on LPO activity were investigated. Ki values were calculated for each indazole molecule. Ki values were ranging from 4.10 to 252.78 µM for 1a to10a. All of the indazole molecules we studied showed strong inhibitory effect on LPO activity. Also we determined inhibition types of the indazoles to clarify the mechanisms of inhibition.